氢气环境下2205双相不锈钢的氢致开裂研究

Hydrogen⁃Induced Cracking of 2205 Duplex Stainless Steel in Hydrogen Environment

为了研究氢气环境下双相不锈钢疲劳裂纹萌生和扩展的影响规律,建立氢气环境下双相不锈钢疲劳应变组织演化—氢致开裂之间的关联机制,在5 MPa氢气和5 MPa氮气2种环境中对2205双相不锈钢试样进行了慢应变速率拉伸和疲劳裂纹扩展速率试验。结果表明:在氢气环境下,2205双相不锈钢在慢应变速率拉伸过程中的氢脆敏感性不高,而在疲劳过程中氢脆现象显著,5 MPa氢气环境下2205双相不锈钢的疲劳裂纹扩展速率比氮气环境中的快18倍;氢气能够促进2205双向不锈钢疲劳裂纹尖端周围组织的局部塑性变形,并进一步导致氢致开裂。在氢气环境下2205双相不锈钢疲劳变形过程中,不同的相结构其氢致开裂机理也不同,铁素体相容易形成河流状花样断口形貌(解理断口),而奥氏体相断口形貌多呈现平行的滑移带特征,奥氏体相在铁素体相的解理开裂过程中对裂纹具有阻碍作用。

In order to study the influence of hydrogen environment on the initiation and propagation of fatigue cracks in duplex stainless steel and establish the correlation mechanism between the fatigue strain microstructure evolution and hydrogen induced cracking in hydrogen environment,slow strain rate tensile and fatigue crack growth rate tests were carried out on 2205 duplex stainless steel specimens in 5 MPa hydrogen and 5 MPa nitrogen environments.Results showed that the hydrogen embrittlement sensitivity of 2205 duplex stainless steel was not high in the process of slow strain rate tensile in hydrogen environment,while it was significant during the fatigue process.The fatigue crack growth rate of 2205 duplex stainless steel in a hydrogen environment of 5 MPa was 18 times higher than that in a nitrogen environment.Hydrogen could promote local plastic deformation around the fatigue crack tip of 2205 duplex stainless steel and further led to hydrogen⁃induced cracking.In the process of fatigue deformation of 2205 duplex stainless steel in a hydrogen environment,different phase structures had different hydrogen⁃induced cracking mechanisms.The ferrite phase was easy to form a river⁃like pattern fracture morphology(cleavage fracture),while the austenite phase fracture appearance mostly presented the characteristics of parallel slip bands.Austenite phase hindered cracks during the cleavage and cracking process of the ferrite phase.